How to reduce noise in a photo

Reduce noise in six steps

1. 1

   Open the photo and zoom to 100%

   Open the photo with File› then Open… (Ctrl+O or ⌘O); to follow along, open the sample from this page. Press Ctrl+1 or ⌘1 (View› then Actual Size (100%)) and pan to a dark, flat area, such as the night sky or a shaded wall, and to an area with fine detail, such as window frames. Noise and its removal can only be judged at 100%.

2. 2

   Convert the layer to a Smart Object

   Choose Layer› then Smart Objects› then Convert to Smart Object. The filter then stays editable as a Smart Filter, so you can lower it later if the photo looks too smooth in print or on a large screen.

   

3. 3

   Choose Filter › Noise › Reduce Noise…

   The Noise submenu holds the cleanup filters: Reduce Noise… for everyday grain, Wavelet Denoise… for finer control, and Despeckle and Dust & Scratches… for isolated specks.

   

4. 4

   Remove the color noise first

   Raise Reduce Color Noise (it starts at 0%) and watch the dark wall and sky: the red, green and blue speckles melt into the surrounding color. Go all the way to 100%: on the sample it leaves about half as much fine color speckle as 80%, with the same gray detail. Colors at edges stay put, because the filter follows the brightness edges of the photo while it smooths the color.

   

5. 5

   Reduce the grain, then protect the detail

   Strength (0–10, default 5) smooths the gray grain: higher values smooth more and over a larger area. Raise it until flat areas look calm, on the sample 6, and stop before textures such as brick, foliage and stone turn into flat patches.

   Protect Detail (default 0%) blends some of the original grain back, which keeps fine texture and edges from looking plastic. 10–30% is a good range; on the sample, 20%.

   Turn Preview off and on to compare, then click Apply.

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6. 6

   Check for smearing and export

   Look at fine detail at 100%: leaves, stone, hair. If they look like a watercolor, the noise reduction is too strong. The right-hand picture below shows Strength 10 with no detail protection (Reduce Color Noise still 100%): the leaves soften and the dark background goes flat. Lower Strength or raise Protect Detail.

   Then export with File› then Export› then JPEG…, or keep the filter editable with File› then Save As› then Lil Cactus Project… (Ctrl+Shift+S or ⇧⌘S).

   

Wavelet Denoise: more control

Filter› then Noise› then Wavelet Denoise… splits the photo into layers of detail, from the finest grain to broad blotches, and lets you clean them separately for brightness (luminance) and color (chroma).

• Luminance Strength and Chroma Strength (both default 0%): how much grain and how much color noise are removed.
• Luminance Levels (default 1) and Chroma Levels (default 3), from 1 to 6: how many detail scales are cleaned. Higher levels also remove coarser, blotchy noise, at the risk of flattening broader texture.
• Detail Retention (default 25%): keeps more texture, at the cost of leaving more noise.

On the sample, Luminance 60% at 3 levels and Chroma 100% at the default 3 levels smooth the gray grain far more than Reduce Noise, but they also soften fine edges such as the window bars and leave colored blotches on the wall and in the sky; even at Chroma 100% more color noise remains than with Reduce Noise. Wavelet Denoise suits photos where gray grain is the main problem and fine edges matter less. More levels take longer and gave no visible gain on the sample.

Dust, specks and hot pixels

• Despeckle (no settings) moves each pixel most of the way toward the median of its immediate neighbors, which fades single-pixel specks and softens the photo slightly.
• Dust & Scratches… replaces only pixels that differ from their neighborhood’s median by more than Threshold (default 26), within a Radius (default 2 px). Use the smallest radius that removes the specks, and raise Threshold until texture comes back. For scanned prints, see how to restore an old photo.
• Hot pixels in long exposures from a RAW file are best removed when opening it: tick Repair isolated hot pixels in the Camera RAW dialog, where the option is available for the file.

Start from RAW when you can

A camera JPEG has already been noise-reduced and compressed by the camera, so the RAW file holds more to work with. If you have the RAW file, use Color noise and Luminance noise in the Detail group of Filter› then Photographic Development…, on the 16-bit data, before anything else.

Why noise reduction can smear detail

A noise filter averages each pixel with its neighbors, so random grain cancels out. The difficulty is that fine detail, a strand of hair, the edge of a leaf, a brick’s texture, also looks like small, local variation. Good filters average along edges rather than across them, which is why window frames stay sharp. But texture that is as fine and faint as the grain itself is averaged away with it. That is the trade-off Strength and Protect Detail control: more smoothing always costs some texture.

What to do next

• Bring back crispness: how to sharpen a photo without halos.
• Brighten a dark photo: how to fix a dark photo.
• Develop the RAW file instead: how to edit a RAW photo.
• Use a layer mask to reduce noise only in the sky or the shadows.

Coming from another editor

Photoshop

Filter › Noise › Reduce Noise… and Dust & Scratches…, the same menu paths as in Lil Cactus.

GIMP

Filters › Enhance › Noise Reduction… and Filters › Enhance › Wavelet-denoise… In Lil Cactus they are under Filter › Noise.

Noise reduction: questions and answers